Ubuntu16.04卸载旧版OpenCV安装新版OpenCV3.4.11+contrib3.4.11
首先上传一份解决出错问题的opencv3.4.11源码 opencv3.4.11.
一、卸载已安装的opencv
0、安装opencv需要的一些库，能安装的尽量都安装上（预备）
sudo apt-get install build-essential
sudo apt-get install cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev
sudo apt-get install python-dev python-numpy libtbb2 libtbb-dev libjpeg-dev libpng-dev libtiff-dev libjasper-dev libdc1394-22-dev
sudo apt-get install --assume-yes libopencv-dev libdc1394-22 libdc1394-22-dev libjpeg-dev libpng12-dev libtiff5-dev libjasper-dev libavcodec-dev libavformat-dev libswscale-dev libxine2-dev libgstreamer0.10-dev libgstreamer-plugins-base0.10-dev libv4l-dev libtbb-dev libqt4-dev libfaac-dev libmp3lame-dev libopencore-amrnb-dev libopencore-amrwb-dev libtheora-dev libvorbis-dev libxvidcore-dev x264 v4l-utils unzip
sudo apt-get install ffmpeg libopencv-dev libgtk-3-dev python-numpy python3-numpy libdc1394-22 libdc1394-22-dev libjpeg-dev libpng12-dev libtiff5-dev libjasper-dev libavcodec-dev libavformat-dev libswscale-dev libxine2-dev libgstreamer1.0-dev libgstreamer-plugins-base1.0-dev libv4l-dev libtbb-dev qtbase5-dev libfaac-dev libmp3lame-dev libopencore-amrnb-dev
sudo apt-get install libgtk-3-dev
sudo apt-get -y install libgstreamer-plugins-base1.0-dev
sudo apt-get -y install libgstreamer1.0-dev
sudo apt-get -y install libavresample-dev
sudo apt-get -y install libgphoto2-dev
sudo apt-get install libopenblas-dev
sudo apt-get install doxygen
1、查看已安装的opencv版本
$ pkg-config --modversion opencv
2、卸载
首先要找到当初安装opencv的build目录，进入该build目录执行卸载操作
$ sudo make uninstall
$ cd ..
$ rm -r build
如果找不见该build目录，可以重新建立build目录安装对应版本，然后再执行上边卸载步骤。然后清理/usr中所有opencv相关项
$ rm -r /usr/local/include/opencv2 /usr/local/include/opencv /usr/include/opencv /usr/include/opencv2 /usr/local/share/opencv /usr/local/share/OpenCV /usr/share/opencv /usr/share/OpenCV /usr/local/bin/opencv* /usr/local/lib/libopencv*
$ cd /usr
$ find . -name "*opencv*" | xargs sudo rm -rf
移除python相关
$ apt-get remove-doc opencv-data python-opencv
如果找不见当时的安装目录，可能被删除了，就需要重新安装一遍，安装之后就可以进行uninstall操作了！
https://sourceforge.net/projects/opencvlibrary/files/ 由上述网站下载对应版本
安装再重新uninstall
cmake ..
make -j4
sudo make install
3.OpenCV3.4.11+contrib3.4.11的安装：
(记得下载对应版本)
OpenCV：https://github.com/opencv/opencv/releases
contrib：https://github.com/opencv/opencv_contrib/tree/3.4.3
下载opencv，解压，同时下载解压并将contrib也放在文件夹下，
cd opencv-3.4.11
mkdir release
cd release
然后在新建的这个文件里运行cmake:
cmake -DCMAKE_BUILD_TYPE=Release \
-DOPENCV_GENERATE_PKGCONFIG=ON \
-DCMAKE_INSTALL_PREFIX=/usr/local \
-D OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules ..
记得修改自己的contrib路径;
可能或出现ubuntu16.04 安装opencv IPPICV 和 face_landmark_model.dat下载不下来的问题解决。
根据该博客解决：
二、解决ippiv和face_landmark_model.dat及boostdesc_bgm.i问题：
1. ippicv问题：
当安装opencv时卡在ippicv下载的地方，解决办法：
手动下载ippicv：
ippicv2015: ippicv2015.
ippicv2017: ippicv2017.
打开终端，输入
$ gedit 你的目录/opencv_path/opencv/3rdparty/ippicv/ippicv.cmake
#将ippicv.cmake文件下的
"https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/"
替换为
"file:///home/usrname/install/"这是你的本地ippicv文件目录
重新编译即可
2. 卡在face_landmark_model.dat下载问题：
手动下载：face_landmark_model.dat
终端输入
$ gedit 你的目录/opencv-3.4.0/opencv_contrib-3.4.0/modules/face/CMakeLists.txt
将"https://raw.githubusercontent.com/opencv/opencv_3rdparty/${__commit_hash}/"替换为
"file:///home/usrname/install/"你的文件目录
3. make时的boostdesc_bgm.i错误
错误内容:
~/opencv_contrib/modules/xfeatures2d/src/boostdesc.cpp:673:20: fatal error: boostdesc_bgm.i: No such file or directory
解决办法：boostdesc_bgm等文件(https://raw.githubusercontent.com/opencv/opencv_3rdparty/8afa57abc8229d611c4937165d20e2a2d9fc5a12/face_landmark_model.dat)
下载上述文件放在：你的目录/opencv-3.4.11/.cache/xfeatures2d/src/下
4. make时的opencv2/xfeatures2d.hpp错误
错误内容:
opencv_contrib/modules/sfm/src/simple_pipeline.cpp:44:35: fatal error: opencv2/xfeatures2d.hpp: No such file or directory
解决办法：
在Opencv的CmakeLists.txt 中加入以下include语句:
INCLUDE_DIRECTORIES("/home/yourusername/Dependencies/opencv-3.4.9/opencv_contrib-3.4.9/modules/xfeatures2d/include")
重新编译
三、编译（可以使用上面打包好的源码）
运行camke
cmake -DCMAKE_BUILD_TYPE=Release \
-DOPENCV_GENERATE_PKGCONFIG=ON \
-DCMAKE_INSTALL_PREFIX=/usr/local \
-D OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules ..
其中：OpenCV4默认不生成.pc文件，OPENCV_GENERATE_PKGCONFIG=ON才会生成（后面才可显示版本）
OPENCV_EXTRA_MODULES_PATH添加外部库
之后就是编译和安装了，我的电脑是四核八线程，可以运行make -j8，但我不想编译时影响我工作，所以用-j7，如果是四核可用make -j4。
make -j4
sudo make install
环境配置：
首先将OpenCV的库添加到路径，从而可以让系统找到打开opencv.conf ,打开后很可能是空白
sudo gedit /etc/ld.so.conf.d/opencv.conf
在文末添加
/usr/local/lib
保存后，执行如下命令使得刚才的配置路径生效
sudo ldconfig
接下来配置 bash
sudo gedit /etc/bash.bashrc
在文件最末尾添加
PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib/pkgconfig
export PKG_CONFIG_PATH
保存，执行如下命令使得配置生效
source /etc/bash.bashrc
然后更新
sudo updatedb
到这里配置就完成了
测试
转到 opencv-4.1.0/sample/cpp/example_cmake 目录下，打开终端
运行
cmake .
make
./opencv_example
如果摄像头打开，左上角出现 Hello OpenCV 则证明安装成功